The invention relates to a length-adjustable upper steering arm for a three-point coupling device for connecting agricultural implements to a tractor, having a sleeve whose ends, inside, are provided with threaded bores whose threads extend in opposite directions and into which a connecting eye or coupling hook comprising a threaded shank with a corresponding thread is screwed so as to be adjustable. The sleeve is provided with a pivotable actuating lever via which, for locking purposes, a locking ratchet may be moved through an aperture in the sleeve into a groove of the threaded shank of the connecting eye or coupling hook.
With such a design, the locking ratchet is rigidly connected to an actuating lever and there is a risk that when the steering arm is adjusted by rotating the sleeve or when transferring or looking for the groove for achieving the locking position, the thread subject to locking ratchet loads may be deformed as a result of the application of the manual force because the coinciding positions of the groove and locking ratchet have to be found by trial and error so that even unintentionally force may be applied to the adjoining thread portion.
Such deformation may adversely affect the functioning ability of the adjusting means.